Permian Record of Gondwanan Environmental Change: From Severe Icehouse to Hothouse and Biotic Crisis

The Permian stratigraphic succession of Gondwana records virtually the full range of climate states known from the Phanerozoic, beginning in a severe Icehouse regime, and ending in a Hothouse regime that heralded the most damaging biotic crisis in Earth history. This paper will review Gondwanan Permian stratigraphy in the context of global environmental change, with emphasis on the eastern Australian record. The beginning of the Permian period witnessed an abrupt and high-magnitude swing from the possible Greenhouse climate mode of the latest Pennsylvanian into severe Icehouse, with bipolar glaciation and widespread ice center coverage in Gondwana. Glacial ice coverage decreased significantly towards the end of the Early Permian and collapsed entirely in some areas. But preservation of Middle Permian glacigenic successions in eastern Australia and southern Africa suggest that the late Paleozoic Ice Age continued to influence Earth surface systems until the close of the Guadalupian. The Late Permian succession includes extensive and thick coal-bearing successions across Gondwana, and preserves a record of fluctuating, everwet to more seasonal climate. Termination of marine faunas in Panthalassan margin basins occurred significantly earlier than the Permo-Triassic boundary, due to an increase in sediment supply relative to accommodation and consequent occlusion of marine environments. In these basins, the latest Permian and Early Triassic succession is predominantly alluvial in origin. The placement of the Permian-Triassic boundary in parts of Gondwana is controversial. According to some authors, the boundary corresponds to an abrupt change in facies from drab, coal-bearing alluvial strata to reddened alluvium, but the biostratigraphic boundary lies within the red alluvial succession and does not seem to coincide with any substantial stratigraphic change. Nonetheless, a Gondwana-wide change to dryland fluvial systems at or around the Permo-Triassic boundary suggests a major reorganization of terrestrial environments that is consistent with the better-known marine system changes.